The present invention relates to an apparatus and method for testing the contents of a sealed container holding a liquid under the pressure of gas in a headspace. The container is typically a can and the liquid may for example be a beverage in which gas is dissolved.
It is the practice in the soft drinks industry to test the contents of a small proportion of cans filled with typically a carbonated beverage during a production run. One of the tests made is to measure the pressure in the headspace of the can to indicate the carbonation of the beverage. Another test is to measure the dissolved oxygen concentration of the beverage. It is necessary for the dissolved oxygen concentration of the beverage to be below a given maximum as oxygen may react with substances in the beverage to cause deterioration of the beverage.
Conventionally, the two tests mentioned above are conducted separately. The can is pierced with a hollow needle having a relatively wide bore. The needle communicates with the pressure gauge. An inner steel tube is inserted through the needle into the liquid in the can and acts as a siphon for withdrawing a sample of the liquid for a measurement of its dissolved oxygen concentration. This arrangement has a disadvantage in that the needle and its associated tubes add appreciably to the volume of the headspace of the can and thus causes inaccuracy in the measurement of the pressure in the headspace.
It is an aim of the invention to provide a method and apparatus that makes it possible to mitigate this problem.